s390/pci: Do not try re-enabling load/store if device is disabled

If a device is disabled unblocking load/store on its own is not useful
as a full re-enable of the function is necessary anyway. Note that SCLP
Write Event Data Action Qualifier 0 (Reset) leaves the device disabled
and triggers this case unless the driver already requests a reset.

Cc: stable@vger.kernel.org
Fixes: 4cdf2f4e ("s390/pci: implement minimal PCI error recovery")
Reviewed-by: Farhan Ali <alifm@linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>